Acoustic and elastic properties of silicone oil under high pressure

Abstract

Brillouin scattering spectra of three silicone oils with different viscosity, including two polydimethylsiloxanes (PDMS) and one polyphenylmethylsiloxane (PPMS), have been studied under high pressure. The acoustic velocity changes of the three silicone oils were measured under pressure and the velocity of all the samples increases with increasing pressure in a similar way. The morphology of the PDMS changed upon compression, possibly accompanied with structural rearrangement or relaxation, but no morphology variation was observed in the PPMS. Based on velocity measurements, the refractive index, density and bulk modulus of the three silicone oils were obtained and the corresponding pressure dependences were compared with some other micro molecule liquids. Obvious differences were observed and discussed. The results indicate that more complicated interactions between the long-chain molecules in silicone oils might result in the larger bulk modulus when compared with the micro molecular liquids.